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July 17, 2012 -- Massachusetts General tops U.S. News & World Report's 2012 list of the best U.S. hospitals, knocking Johns Hopkins out of the top spot it's held for 21 years.

The rankings, produced by RTI International, are based on several factors:

Patient survival. On a 1-to-10 scale, this score accounts for 32.5% of a hospital's ranking.

Reputation. Two hundred doctors in each specialty are randomly selected and asked to list the hospitals they think are best in their specialty for complex or difficult cases. This accounts for 32.5% of a hospital's ranking.

Patient safety score. Hospitals are rated on how well they work to prevent the worst kinds of harmful blunders. This accounts for 5% of a hospital's ranking.

Other factors. Care-related factors such as nurse staffing, technology, and other factors linked to quality care account for 30% of a hospital's ranking.

This year, 17 hospitals made the list's honor role. These are hospitals that score at or near the top in at least six of the 16 specialties considered in the ratings.

The honor roll:

Massachusetts General Hospital, Boston

Johns Hopkins Hospital, Baltimore

Mayo Clinic, Rochester, Minn.

Cleveland Clinic

Ronald Reagan UCLA Medical Center, Los Angeles

Barnes-Jewish Hospital/Washington University, St. Louis

New York Presbyterian University Hospital of Columbia and Cornell, N.Y.

Duke University Medical Center, Durham, N.C.

Brigham and Women's Hospital, Boston

UMPC University of Pittsburgh Medical Center

NYU Langone Medical Center, New York

Northwestern Memorial Hospital, Chicago

UCSF Medical Center, San Francisco

Mount Sinai Medical Center, New York

Hospital of the University of Pennsylvania, Philadelphia

Indiana University Health, Indianapolis

University of Michigan Hospitals and Health Centers, Ann Arbor

The ratings also listed the best hospitals for major medical specialties. The winners in each category: